Poor early virologic performance and durability of abacavir-based first-line regimens for HIV-infected children

Safety and efficacy of abacavir for treating infants, children, and adolescents living with HIV: a systematic review and meta-analysis

BACKGROUND

Abacavir is a nucleoside reverse transcriptase inhibitor recommended in paediatric HIV care. We assessed the safety and efficacy profile of abacavir used in first, second, or subsequent lines of treatment for infants, children, and adolescents living with HIV to inform 2021 WHO paediatric ART recommendations.

METHODS

In this systematic review and meta-analysis, we included observational and experimental studies conducted in infants aged 0-1 year, children aged 1-10 years, and adolescents aged 10-19 years living with HIV; with data on safety or efficacy, or both, of abacavir-based antiretroviral therapy (ART); published in English or French between Jan 1, 2009, and Oct 1, 2020, plus an updated search to incorporate studies published between Oct 1, 2020, and May 15, 2022. Studies could be non-randomised or non-comparative and include patients who are treatment-naive or those who previously received abacavir (only if abacavir was combined with other ART). Case studies, studies in adults aged 18 years or older, and those assessing the effect of maternal ART exposure were excluded. We extracted data related to study identifier, study design, study period, setting, population characteristics, ART treatment, and safety (any hypersensitivity reaction, death, grade 3 or 4 adverse events, treatment discontinuation, any other morbidities, and serious adverse events), and efficacy outcomes (HIV viral load and CD4 counts reported at 6 and 12 months after ART initiation). Using random-effect models, we estimated weighted pooled incidence and relative risk (RR) of outcomes. The protocol is published in PROSPERO (CRD42022309230).

FINDINGS

Of 1777 records identified, 1475 (83%) were screened after removing duplicates and a further 1421 (96%) were excluded. Of 54 full-text articles assessed for eligibility, 33 (61%) were excluded. Four records were identified from grey literature plus one duplicate from database searching, resulting in 24 studies included (two randomised controlled trials, one single-arm trial, 12 prospective cohorts, seven retrospective cohorts, and two cross-sectional studies). 19 studies described safety data and 15 described efficacy data. 18 (75%) studies were conducted in ART-naive participants. The risk of bias was considered moderate to high for most studies, and all outcomes had significant between-study heterogeneity. Data from 24 265 participants were included, of whom 7236 (30%) received abacavir. Abacavir hypersensitivity reaction was reported in nine (38%) studies, with an incidence ranging from 0·00% to 8·26% (I2=85%; p<0·0001). The incidence of death (reported in seven studies) following abacavir treatment varied from 0·00% to 5·49% (I2=58%; p=0·026). Viral suppression (<400 copies per mL) varied from 50% to 70% at 6 months (I2=92%, p<0·0001) and from 57% to 78% at 12 months (I2=88%, p<0·0001).

INTERPRETATION

Toxic effects due to abacavir use remain rare and manageable. Despite scarce data on efficacy, this meta-analysis supports the use of abacavir as a preferred first-line regimen for infants and children living with HIV.

FUNDING

WHO.

Viral suppression among adolescents on HIV treatment in the Sedibeng District, Gauteng province

BACKGROUND

 Progress has been made to increase access to antiretroviral therapy (ART) for adolescents living with HIV (ALHIV) to improve their survival, but ALHIV still have worse treatment adherence and viral suppression compared to adults and children.

OBJECTIVE

 To determine the prevalence of viral suppression and the associated factors among adolescents aged 10-19 years on ART at an urban public primary healthcare facility in the Sedibeng district, Gauteng.

METHOD

 A cross-sectional survey was conducted among 192 adolescents who were on ART for at least six months between 2015 and 2018. A self-developed data extraction tool was used to collect data from the Tier.Net electronic database and clinical folders. Data were captured on Microsoft Excel, and descriptive and inferential analyses were performed using SPSS 27 statistical software.

RESULTS

 The median age at ART initiation of adolescents was 9.0 years (interquartile range [IQR]: 5.0-12.0), and the median duration on ART was 70.5 (IQR: 30.25-105.5) months. The prevalence of viral suppression ( 1000 copies/mL) among adolescents on ART was 74%, with 41% achieving full suppression ( 50 copies/mL). Those adolescents who reported optimal ART adherence were more likely to be virally suppressed compared to those who reported poor adherence (98.1% vs 25.0%; p ≤ 0.001).

CONCLUSION

 Adolescent viral suppression of 74% is higher than in comparable sites, but still way too short of the UNAIDS target of 90%. We recommend adherence support for adolescents to achieve viral suppression.Contribution: The study highlights the urgent need for targeted adherence support interventions for adolescents living with HIV on antiretroviral therapy to improve rates of viral suppression to meet UNAIDS target of 95%.

Association of Antiretroviral Drug Regimen With Viral Suppression in HIV-positive Children on Antiretroviral Therapy in Eswatini

BACKGROUND

Global pediatric treatment goals are for 90% of known children living with HIV to be on antiretroviral therapy (ART), with 90% having viral suppression. We used enrollment data from a study evaluating a family-centered HIV care program in Eswatini to describe the ART histories and virologic outcomes of enrolled children living with HIV and identify factors associated with viral suppression (<1000 RNA copies/mL) and undetectability (<400 RNA copies/mL).

METHODS

Factors associated with viral suppression and undetectability were identified using Pearson χ for categorical variables and Wilcoxon rank sum tests for continuous variables.

RESULTS

Three hundred seventy-seven children were enrolled, median age 8.5 years. Median age at HIV diagnosis was 2.1 years; at ART initiation, 2.6 years; and ART duration at enrollment, 4.1 years. Ninety-nine percent were receiving ART; 95.2% were on first-line ART and 4.8% on second-line ART. Most children (43.1%) were receiving nevirapine-based ART (median age 9.2 years), with 31.3% on lopinavir-ritonavir-based (median age 5.4 years) and 25.5%, efavirenz-based ART (median age 10.3 years). Viral suppression (<1000 copies/mL) was observed in 77.9% and undetectability (<400 copies/mL) in 73.5% of children. The only factor significantly associated with viral suppression was ART regimen, with 72.1% of children on nevirapine-based ART versus 86.7% on efavirenz-based ART virally suppressed.

CONCLUSIONS

Although 99% of children enrolled in the study were receiving ART, viral suppression was observed in only 77.9%, with lowest rates among children receiving nevirapine-based ART. These findings highlight the critical importance of monitoring treatment regimen for optimizing treatment outcomes for pediatric HIV.

Substituting Abacavir for Stavudine in Children Who Are Virally Suppressed Without Lipodystrophy: Randomized Clinical Trial in Johannesburg, South Africa

OBJECTIVES

Abacavir has replaced stavudine in antiretroviral therapy (ART) regimens because it has largely been phased out as a result of toxicity concerns; this loss has reduced further the already-limited drug options for children. Few data regarding virologic and metabolic outcomes among children who undergo substitution of stavudine exist. We evaluated the effects of preemptive substitution of abacavir for stavudine in children initially without lipodystrophy and virally suppressed on a stavudine-containing regimen.

METHODS

At Rahima Moosa Mother and Child Hospital in Johannesburg, South Africa, virally suppressed human immunodeficiency virus (HIV)-infected children ≥36 months of age without lipodystrophy were randomly assigned to continue taking stavudine as part of their ART regimen (n = 106) or to have abacavir substituted for stavudine (n = 107). The children were followed for 56 weeks after randomization in the context of a larger trial of treatment options for ART-experienced children.

RESULTS

The mean age of the children was 4.3 years, and the mean duration of ART before random assignment was 3.5 years. No differences in virological outcomes, CD4 response, growth, or dyslipidemia were noted between the stavudine and abacavir groups. By 56 weeks, children in the abacavir group had less clinically detected lipodystrophy (4.7% vs 16%, respectively), a higher proportion of leg fat relative to total fat (0.243 vs 0.230, respectively; P = .006), and a lower trunk/leg-skinfold ratio (0.547 vs 0.569, respectively; P = .003) than the children in the stavudine group.

CONCLUSION

Substituting abacavir for stavudine did not compromise virological response to treatment and was associated with significantly less lipodystrophy. These results support recommendations that favor abacavir in this population.

High Prevalence of Abacavir-associated L74V/I Mutations in Kenyan Children Failing Antiretroviral Therapy

A survey of 461 HIV-infected Kenyan children receiving antiretroviral therapy found 143 (31%) failing virologically. Drug resistance mutations were found in 121; 37 had L74V/I mutations, with 95% receiving abacavir (ABC)-containing regimens. L74V/I was associated with current ABC usage (P = 0.0001). L74V/I may be more prevalent than previously realized in children failing ABC-containing regimens, even when time on treatment has been short. Ongoing rigorous pediatric drug resistance surveillance is needed.

A retrospective case-cohort study comparing treatment outcomes in abacavir versus stavudine containing first line antiretroviral treatment regimens in children <3yrs old, at a paediatric programme based in Soweto, South Africa

Introduction

The current World Health Organization guideline for first line antiretroviral therapy (ART) in HIV-infected children recommends the use of abacavir and lamivudine as nucleoside backbones and no longer includes stavudine. We compared treatment outcomes with abacavir (ABC) versus stavudine (d4T) in a cohort of HIV-1 infected children 6 and 12 months after antiretroviral therapy was initiated.

Methods

This was a retrospective case-cohort study, using programmatic data from children enrolled in the Paediatric Wellness Programme at the Perinatal HIV Research Unit in Soweto, South Africa between 2005 and 2013. Children on abacavir/stavudine who had initiated ART at age <3 years with a regimen including lamivudine and lopinavir/ritonavir and had at least one 6 or 12 month viral load result were eligible. All ABC cases identified were matched for age at ART initiation and gender to eligible d4T controls (1:2). Outcomes analysed at 6 and 12 months post ART initiation included virological failure, mortality, immunological failure and anthropometry. Chi-square tests compared categorical measures while Kruskal-Wallis compared continuous measures.

Results

We identified 57 eligible ABC cases and selected 114 matched d4T controls. Overall, 57% were females and 89% started treatment at age <1year. The median age at ART initiation was 3.11 (IQR: 1.98–6.05) months. There was no difference in the proportion of children virologically suppressed between the groups at 6 (ABC 54.5% vs. d4T 67.0%, p = 0.125) and 12 (ABC 66.7% vs. d4T 71.6%, p = 0.53) months post ART-initiation. The proportion of children with adherence levels >90% for ABC and d4T were similar too (95% in ABC vs. 86% in d4T, p = 0.10). The proportion of children who died over 12 months was 3.5% in the ABC and 7.9% in the d4T group (p = 0.27). Similarly, the anthropometric measures were comparable.

Conclusions

It is reassuring that in the short term, in this group of patients, the treatment outcomes were similar.

Insights into Adherence among a Cohort of Adolescents Aged 12-20 Years in South Africa: Reported Barriers to Antiretroviral Treatment

Adolescents experience disproportionately high rates of poor ART outcomes compared to adults despite prolonged use of antiretroviral therapy in Southern African treatment programs, presenting a significant challenge to national attempts to meet the UNAIDS 90-90-90 targets for 2020. This cohort study among adolescents aged 12-20 years accessing ART care at two urban public-sector clinics in Johannesburg between September and November 2013 aimed to identify factors potentially associated with poor attendance at clinic visits. Patients were followed up through routine medical records to identify missed visits (failing to attend clinic within 30 days of scheduled visit date) up to 2 years after enrolment. We enrolled 126 adolescents on ART for a median of 6.3 years (IQR: 2.7-8.4). A total of 47 (38%) adolescents missed a scheduled visit within 24 months of enrolment. Older adolescents (18-20 years) were more likely to miss a visit compared to adolescents aged 12-14 years (risk ratio (RR) = 1.72; 95% CI: 1.00-2.95). Those who were identified to have difficulty in taking medication (RR = 1.57; 95% CI: 1.13-2.18) as a barrier to care were more likely to miss a visit compared to adolescents who did not. Awareness of treatment fatigue, challenges to taking ART, and caregiver difficulties is important when considering interventions to improve treatment outcomes among adolescents.

A 10-year cohort analysis of routine paediatric ART data in a rural South African setting

South Africa's paediatric antiretroviral therapy (ART) programme is managed using a monitoring and evaluation tool known as TIER.Net. This electronic system has several advantages over paper-based systems, allowing profiling of the paediatric ART programme over time. We analysed anonymized TIER.Net data for HIV-infected children aged <15 years who had initiated ART in a rural district of South Africa between 2005 and 2014. We performed Kaplan–Meier survival analysis to assess outcomes over time. Records of 5461 children were available for analysis; 3593 (66%) children were retained in care. Losses from the programme were higher in children initiated on treatment in more recent years (P < 0·0001) and in children aged ≤1 year at treatment initiation (P < 0·0001). For children aged <3 years, abacavir was associated with a significantly higher rate of loss from the programme compared to stavudine (hazard ratio 1·9, P < 0·001). Viral load was suppressed in 48–52% of the cohort, with no significant change over the years (P = 0·398). Analysis of TIER.Net data over time provides enhanced insights into the performance of the paediatric ART programme and highlights interventions to improve programme performance.

Abacavir, zidovudine, or stavudine as paediatric tablets for African HIV-infected children (CHAPAS-3): an open-label, parallel-group, randomised controlled trial

BACKGROUND

WHO 2013 guidelines recommend universal treatment for HIV-infected children younger than 5 years. No paediatric trials have compared nucleoside reverse-transcriptase inhibitors (NRTIs) in first-line antiretroviral therapy (ART) in Africa, where most HIV-infected children live. We aimed to compare stavudine, zidovudine, or abacavir as dual or triple fixed-dose-combination paediatric tablets with lamivudine and nevirapine or efavirenz.

METHODS

In this open-label, parallel-group, randomised trial (CHAPAS-3), we enrolled children from one centre in Zambia and three in Uganda who were previously untreated (ART naive) or on stavudine for more than 2 years with viral load less than 50 copies per mL (ART experienced). Computer-generated randomisation tables were incorporated securely within the database. The primary endpoint was grade 2-4 clinical or grade 3/4 laboratory adverse events. Analysis was intention to treat. This trial is registered with the ISRCTN Registry number, 69078957.

FINDINGS

Between Nov 8, 2010, and Dec 28, 2011, 480 children were randomised: 156 to stavudine, 159 to zidovudine, and 165 to abacavir. After two were excluded due to randomisation error, 156 children were analysed in the stavudine group, 158 in the zidovudine group, and 164 in the abacavir group, and followed for median 2·3 years (5% lost to follow-up). 365 (76%) were ART naive (median age 2·6 years vs 6·2 years in ART experienced). 917 grade 2-4 clinical or grade 3/4 laboratory adverse events (835 clinical [634 grade 2]; 40 laboratory) occurred in 104 (67%) children on stavudine, 103 (65%) on zidovudine, and 105 (64%), on abacavir (p=0·63; zidovudine vs stavudine: hazard ratio [HR] 0·99 [95% CI 0·75-1·29]; abacavir vs stavudine: HR 0·88 [0·67-1·15]). At 48 weeks, 98 (85%), 81 (80%) and 95 (81%) ART-naive children in the stavudine, zidovudine, and abacavir groups, respectively, had viral load less than 400 copies per mL (p=0·58); most ART-experienced children maintained suppression (p=1·00).

INTERPRETATION

All NRTIs had low toxicity and good clinical, immunological, and virological responses. Clinical and subclinical lipodystrophy was not noted in those younger than 5 years and anaemia was no more frequent with zidovudine than with the other drugs. Absence of hypersensitivity reactions, superior resistance profile and once-daily dosing favours abacavir for African children, supporting WHO 2013 guidelines.

FUNDING

European Developing Countries Clinical Trials Partnership.

Efficacy and safety of abacavir-containing combination antiretroviral therapy as first-line treatment of HIV infected children and adolescents: a systematic review and meta-analysis

BACKGROUND

Abacavir is one of the recommended nucleoside reverse transcriptase inhibitors (NRTIs) for the treatment of HIV infections among children and adolescents. However, there are concerns that the antiviral efficacy of abacavir might be low when compared to other NRTIs especially among children. There are also concerns that abacavir use may lead to serious adverse events such as hypersensitivity reactions and has potential predisposition to developing cardiovascular diseases

METHODS

We searched four electronic databases, four conference proceedings and two clinical trial registries in August 2014, without language restrictions. Experimental and observational studies with control groups that examined the efficacy and safety of abacavir-containing regimens in comparison with other NRTIs as first-line treatment for HIV-infected children and adolescents aged between one month and eighteen years were eligible. Two authors independently screened search results, extracted data and assessed the risk of bias of included studies using a pre-specified, standardised data extraction form and validated risk of bias tools. We also assessed the quality of evidence per outcome with the GRADE tool.

RESULTS

We included two randomised controlled trials (RCTs) and two analytical cohort studies with a total of 10,595 participants. Among the RCTs we detected no difference in virologic suppression after a mean duration of 48 weeks between abacavir- and stavudine-containing regimens (2 trials; n = 326: RR 1.28; 95 % CI 0.67-2.42) with significant heterogeneity (P = 0.02; I(2) = 81 %). We also found no significant differences between the two groups for adverse events and death. After five years of follow-up, virologic suppression improved with abacavir (1 trial; n = 69: RR 1.96; 95 % CI 1.11-3.44). For cohort studies, we detected that the virologic suppression activity of abacavir was less effective than stavudine in both the lopinavir/ritonavir (1 study, n = 2165: RR 0.79, 95 % CI 0.67-0.92) and efavirenz sub-groups (1 study, n = 3204: RR 0.79, 95 % CI 0.67-0.92) respectively. The quality of evidence from RCTs was moderate for virologic suppression but low for death and adverse events, while that of cohort studies was low for all three these outcomes.

CONCLUSIONS

Available evidence showed little or no difference between abacavir-containing regimen and other NRTIs regarding efficacy and safety when given to children and adolescents as a first-line antiretroviral therapy.

Impact of earlier combination antiretroviral therapy on outcomes in children

PURPOSE OF REVIEW

Early initiation of combination antiretroviral therapy (ART) in infants below 12 weeks of age reduces morbidity and mortality. A recent report of transient HIV remission in a child beginning ART from the second day of life has focused attention on very early therapy in the first days of life.

RECENT FINDINGS

In the randomized children with HIV, early antiretroviral limited ART beginning at a median of 7.4 weeks of age lowered mortality and disease progression significantly compared with deferred ART beginning at a median of 21 weeks on study. In high-burden settings, infants initiating ART appear sicker than in children with HIV early antiretroviral and start at a later age. Many could be diagnosed on the first day of life. There are still programmatic obstacles to early diagnosis and initiation of ART in high-burden settings. There is growing but insufficient information on ART dosages in newborn infants.

SUMMARY

There is now increased focus on initiating ART as postexposure prophylaxis in newborn infants at high risk of vertical transmission in the hope of limiting morbidity and dissemination of the virus.

Tackling virological failure in HIV-infected children living in Africa

Drug resistance in HIV-infected children is one of the main contributors to antiretroviral treatment (ART) failure, especially in developing countries. Sub-Saharan Africa has the largest burden of pediatric HIV infection in the world. Herein, we systematically review the current status of ART failure in HIV-infected African children. A literature search for publications within 10 years was performed through PubMed to identify relevant articles. Included studies examined the impact of timing of ART initiation, criteria for diagnosing therapeutic failure, predictors of therapeutic failure, management strategies and future directions to minimize failure rates in these pediatric populations. Although there is scale-up of ART programs in Africa, novel therapeutic and management strategies are needed to overcome current challenges.

Effect of reducing the paediatric stavudine dose by half: a physiologically-based pharmacokinetic model

Owing to significant dose-related toxicity, the adult stavudine dose was reduced in 2007. The paediatric dose, however, has not been reduced. Although the intended paediatric dose is 1 mg/kg twice daily (b.i.d.), the current weight-band dosing approach results in a mean actual dose of 1.23±0.47 mg/kg. Both efficacy and mitochondrial toxicity depend on the concentration of the intracellular metabolite stavudine triphosphate (d4T-TP). We simulated the effect of reducing the paediatric dose to 0.5 mg/kg. A physiologically-based pharmacokinetic model consisting of 13 tissue compartments plus a full ADAM model was used to describe the elimination of stavudine. The volume of distribution at steady-state and apparent oral clearance were simulated and the resulting AUC profile was compared with literature data in adult and paediatric populations. A biochemical reaction model was utilised to simulate intracellular d4T-TP levels for both the standard and proposed reduced paediatric doses. Simulated and observed exposure after oral dosing showed adequate agreement. Mean steady-state d4T-TP for 1.23 mg/kg b.i.d. was 27.9 (90% CI 27.0-28.9) fmol/10(6) cells, 25% higher than that achieved by the 40 mg adult dose. The 0.5 mg/kg dose resulted in d4T-TP of 13.2 (12.7-13.7) fmol/10(6) cells, slightly higher than the adult dose of 20 mg b.i.d. [11.5 (11.2-11.9) fmol/10(6) cells], which has excellent antiviral efficacy and substantially less toxicity. Current paediatric dosing may result in even higher d4T-TP than the original 40 mg adult dose. Halving the paediatric dose would significantly reduce the risk of mitochondrial toxicity without compromising antiviral efficacy.

Predictors of Treatment Failure in HIV-Positive Children Receiving Combination Antiretroviral Therapy: Cohort Data From Mozambique and Uganda

BACKGROUND

Delays detecting treatment failure and switching to second-line combination antiretroviral therapy (cART) are often observed in human immunodeficiency virus (HIV)-infected children of low-middle-income countries (LMIC).

METHODS

An observational study included HIV-infected children attending the Beira Central Hospital (Mozambique) and the Nsambya Hospital, Home Care Department (Uganda) evaluated clinical and immunological failure according to World Health Organization (WHO) 2006 guidelines. Baseline predictors for cART failure and for drug substitution were explored in unadjusted and adjusted Cox proportional hazard models.

RESULTS

Two hundred eighteen of 740 children with at least 24 weeks follow-up experienced treatment failure (29%; 95% confidence interval [CI] 26-33), with crude incidence of 20.0 events per 100 person-years (95% CI 17.5-22.9). Having tuberculosis co-infection or WHO stage 4, or starting a nontriple cART significantly increased risk of failure. Two hundred two of 769 (26.3%) children receiving cART substituted drug(s), with crude incidence of 15.4 events per 100 person-years (95% CI 13.4-17.7). Drug toxicity (18.3%), drug availability (17.3%), and tuberculosis drugs interaction (52, 25.7%) were main reported reasons, while only 9 (4%) patients switched cART for clinical or immunological failure. Children starting lamivudine-zidovudine-nevirapine or lamivudine-stavudine-efavirenz or lamivudine-zidovudine-efavirenz were more likely to have substitute drugs. Increased substitution was found in children with mild immunosuppression and tuberculosis co-infection at cART initiation as well as poor adherence before drug substitution.

CONCLUSIONS

Considerable delay in switching to second-line cART may occur despite an observed high rate of failure. Factors including WHO clinical stage and tuberculosis co-infection should be evaluated before starting cART. Toxicity and drug adherence should be monitored to minimize drug substitution in LMIC.

Antiviral efficacy and safety of abacavir-containing combination antiretroviral therapy as first-line treatment of HIV-infected children and adolescents: a systematic review protocol

BACKGROUND

Abacavir is one of the recommended nucleoside reverse transcriptase inhibitors (NRTIs) for the treatment of HIV infections among children and adolescents. However, there are concerns that the antiviral efficacy of abacavir might be low when compared to other NRTIs especially among children. There are also concerns that abacavir use may lead to serious adverse events such as hypersensitivity reactions and has potential predisposition to developing cardiovascular diseases.

METHODS

We plan to do a systematic review to evaluate the antiviral efficacy and safety of abacavir-containing combination antiretroviral therapy as first-line treatment of HIV-infected children aged between 3 months and 18 years, compared with other NRTIs. We will search Scopus, Cochrane Central Register of Controlled Trials, MEDLINE, and Web of Science databases for eligible studies regardless of language or publication status. We will check the reference lists of included studies, search relevant conference proceedings, email the authors of included studies and also look for unpublished and ongoing trials in prospective clinical trial registries. Two authors will independently screen search outputs, select studies, extract data and assess the risk of bias in included studies. All disagreements will be resolved by discussion and consensus. Where data allow, we will conduct meta-analysis for similar types of participants, study designs, interventions, and outcome measures. If the results are statistically homogeneous, we will use the fixed-effect model; otherwise, we will use the random-effects model and explore the reasons for heterogeneity using subgroup analyses. Heterogeneity will be assessed with the Chi-squared test and quantified with the I-squared statistic.

DISCUSSION

The findings will be useful to policy makers and programme managers to inform treatment and management of HIV in children and adolescents and to point out research gaps for future research.

TRIAL REGISTRATION

This review is registered with PROSPERO, registration number CRD42014009157.

Virologic response in children treated with abacavir-compared with stavudine-based antiretroviral treatment: a South African multi-cohort analysis

BACKGROUND

Initiation criteria and pediatric antiretroviral treatment regimens have changed over the past few years in South Africa. We reported worse early virological outcomes associated with the use of abacavir (ABC)-based regimens at 1 large site: here, we expand this analysis to multiple sites in the IeDEA-Southern Africa collaboration.

METHODS

Data for 9543 antiretroviral treatment-naïve children <16 years at treatment initiation started on either stavudine/lamivudine (d4T/3TC) or ABC/3TC with efavirenz (EFV) or ritonavir-boosted lopinavir (LPV/r) treated at 6 clinics in Johannesburg and Cape Town, South Africa, were analyzed with χ tests and logistic regression to evaluate viral suppression at 6 and 12 months.

RESULTS

Prevalence of viral suppression at 6 months in 2174 children started on a d4T-based LPV/r regimen was greater (70%) than among 438 children started on an ABC-based LPV/r regimen (54%, P < 0.0001). Among 3189 children started on a d4T-based EFV regimen, a higher proportion (86%) achieved suppression at 6 months compared with 391 children started on ABC-containing EFV regimens (78%, P < 0.0001). Relative benefit of d4T versus ABC on 6-month suppression remained in multivariate analysis after adjustment for pretreatment characteristics, cohort and year of program [LPV/r: odds ratio = 0.57 (confidence interval: 0.46-0.72); EFV: odds ratio = 0.46 (confidence interval: 0.32-0.65)].

CONCLUSIONS

This expanded analysis is consistent with our previous report of worse virological outcomes after ABC was introduced as part of first-line antiretroviral treatment in South Africa. Whether due to the drug itself or coincident with other changes over time, continued monitoring and analyses must clarify causes and prevent suboptimal long-term outcomes.

Estimation of intracellular concentration of stavudine triphosphate in HIV-infected children given a reduced dose of 0.5 milligrams per kilogram twice daily

The antiviral efficacy of stavudine depends on the trough concentration of its intracellular metabolite, stavudine-triphosphate (d4T-TP), while the degree of stavudine's mitochondrial toxicity depends on its peak concentration. Rates of mitochondrial toxicity are high when stavudine is used at the current standard pediatric dose (1 mg/kg twice daily [BID]). Evidence from adult work suggests that half of the original standard adult dose (i.e., 20 mg BID) may be equally effective, with markedly less mitochondrial toxicity. We present a population pharmacokinetic model to predict intracellular d4T-TP concentrations in pediatric HIV-infected patients administered a dose of 0.5 mg/kg BID. Our model predicted that the reduced pediatric dose would result in a trough intracellular d4T-TP concentration above that of the reduced 20-mg adult dose and a peak concentration below that of the 20-mg adult dose. The simulated pediatric intracellular d4T-TP at 0.5 mg/kg BID resulted in median peak and trough values of approximately 23.9 fmol/10(6) cells (95% prediction interval [PI], 14.2 to 41 fmol/10(6) cells) and 14.8 fmol/10(6) cells (95% PI, 7.2 to 31 fmol/10(6) cells), respectively. The peak and trough concentrations resulting from a 20-mg BID adult dose were 28.4 fmol/10(6) cells (95% PI, 17.3 to 45.5 fmol/10(6) cells) and 13 fmol/10(6) cells (95% PI, 6.8 to 28.6 fmol/10(6) cells), respectively. Halving the current standard pediatric dose should therefore not compromise antiviral efficacy, while markedly reducing mitochondrial toxicity.